A liquid crystal panel included in a liquid crystal display device does not emit light, and thus a backlight device is required as a separate lighting device. The backlight device is arranged behind the liquid crystal panel (i.e., on a side opposite from a display surface side). It includes a chassis having an opening on a liquid crystal panel side, a plurality of fluorescent tubes housed in the chassis as a lamp, and an optical member (such as a diffuser plate) that is provided in the opening of the chassis and effectively discharges light emitted from the fluorescent tubes to the liquid crystal panel side.
In such a backlight device where the fluorescent tubes emit linear light, a plurality of fluorescent tubes are aligned with each other and the optical member converts linear light into planer light to unify illumination light. However, if the linear light is not sufficiently converted into the planer light, striped lamp images are generated along the alignment of the fluorescent tubes, and this deteriorates display quality of the liquid crystal display device.
To obtain uniform illumination light from the backlight device, it is desirable to increase the number of lamps and reduce a distance between the adjacent lamps or to increase a diffusion rate of a diffuser plate, for example. However, increase of the number of lamps increases a cost of the backlight device and also increases power consumption. Increase of the diffusion rate of the diffuser plate fails to improve brightness and causes the problem that the number of lamps is required to be increased. A backlight device disclosed in Patent Document 1 has been known as one that suppresses power consumption and ensures uniform brightness.
The backlight device described in Patent Document 1 includes a light source emitting rays of light, a light guide reflecting the rays of light to a liquid crystal display side, light blocking means provided between the light source and the liquid crystal display and on a portion directly above the light source, and a diffuser plate diffusing the rays of entering light to obtain uniform diffused light. The light blocking means blocks a part of the rays of light emitted from the light source.    [Patent Document 1] Japanese Unexamined Utility Model Publication No. 2-69318